Biology subjects

Grignolio, D.

Publications and source records attributed to Grignolio, D..

5 recordsLinked to original sources

bioRxiv2025

Complementary attentional mechanisms for the resolution of representational ambiguity in the human brain

When we view cluttered environments containing multiple objects, the neural code for individual items can become ambiguous. This reflects a capacity limit in spatially-tuned visual neurons: when multiple objects fall within the cell receptive field, output cannot be attributed to a single object. Vision models from primate electrophysiology propose this is resolved by attention, which biases competition between object representations. However, evidence in humans is sparse and inconclusive, and reliance on single-cell data limits insight into underlying mechanisms and neurophysiological scope. Here, we use a novel multivariate approach to the analysis of human EEG and concurrent EEG/MRI to address this. First, we test whether attention is recruited by representational ambiguity. Second, we identify the mechanisms that act on representations of attended and unattended objects to resolve ambiguity. Finally, we characterize the millisecond timing and whole-brain action of these mechanisms to identify pervasive effects in semantic and executive brain networks.

neuroscience↗

bioRxiv2025

Neural Oscillations Coordinate Continuous Error Correction During Force Control

Effective motor control depends on the brains ability to monitor performance and make continuous corrections. While many studies focus on discrete errors, everyday actions often require ongoing feedback-based adjustments. Here, we used an isometric force control task with EEG to investigate the neural dynamics supporting real-time error correction. Participants maintained a constant grip force with or without continuous visual feedback. With feedback, behavior showed [~]6 Hz rhythmic fluctuations, consistent with active correction. These fluctuations were mirrored in EEG activity across theta, beta, and alpha bands--oscillations linked to performance monitoring, updating, and attentional control. Without feedback, performance decayed linearly, and the corresponding neural signatures were reduced. These findings suggest that continuous sensory feedback engages a dynamic feedback loop involving distinct neural processes that support adaptive behavior. Our results highlight the importance of oscillatory activity in tracking and correcting moment-to-moment fluctuations in force, offering insight into the neural basis of feedback-loop force control.

neuroscience↗

bioRxiv2025

Neural mechanisms of object prioritization in vision

Selective attention is widely thought to be sensitive to visual objects. This is commonly demonstrated in cueing studies, which show that when attention is deployed to a known target location that happens to fall on a visual object, responses to targets that unexpectedly appear at other locations on that object are faster and more accurate, as if the object in its entirety has been visually prioritized. However, this notion has recently been challenged by results suggesting that putative object-based effects may reflect the influence of hemifield anisotropies in attentional deployment, or of unacknowledged influences of perceptual complexity and visual clutter. Studies employing measures of behaviour provide limited opportunity to address these challenges. Here, we used EEG to directly measure the influence of task-irrelevant objects on the deployment of visual attention. We had participants complete a simple visual cueing task involving identification of a target that appeared at either a cued location or elsewhere. Throughout each experimental trial, displays contained task-irrelevant rectangle stimuli that could be oriented horizontally or vertically. We derived two cue-elicited indices of attentional deployment-lateralized alpha oscillations and the ADAN component of the event-related potential-and found that these were sensitive to the otherwise irrelevant orientation of the rectangles. Our results demonstrate that the allocation of visual attention is influenced by objects boundaries, supporting models of object-based attentional prioritization.

neuroscience↗

bioRxiv2024

Using N2pc variability to probe functionality: Linear mixed modelling of trial EEG and behaviour

This paper has two concurrent goals. On one hand, we hope it will serve as a simple primer in the use of linear mixed modelling (LMM) for inferential statistical analysis of multimodal data. We describe how LMM can be easily adopted for the identification of trial-wise relationships between disparate measures and provide a brief cookbook for assessing the suitability of LMM in your analyses. On the other hand, this paper is an empirical report, probing how trial-wise variance in the N2pc, and specifically its sub-component the NT, can be predicted by manual reaction time (RT) and stimuli parameters. Extant work has identified a link between N2pc and RT that has been interpreted as evidence of a direct and causative relationship. However, results have left open the less-interesting possibility that the measures covary as a function of motivation or arousal. Using LMM, we demonstrate that the relationship only emerges when the NT is elicited by targets, not distractors, suggesting a discrete and functional relationship. In other analyses, we find that the target-elicited NT is sensitive to variance in distractor identity even when the distractor cannot itself elicit consistently lateralized brain activity. The NT thus appears closely linked to attentional target processing, supporting the propagation of target-related information to response preparation and execution. At the same time, we find that this component is sensitive to distractor interference, which leaves open the possibility that NT reflects brain activity responsible for the suppression of irrelevant distractor information.

neuroscience↗

bioRxiv2024

Attentional propagation of conceptual information in the human brain

The visual environment is complicated, and humans and other animals accordingly prioritise some sources of information over others through the deployment of spatial attention. We presume that attention has the ultimate purpose of guiding the abstraction of information from perceptual experience in the development of concepts and categories. However, neuroscientific investigation has focussed closely on identification of the systems and algorithms that support attentional control, or that instantiate the effect of attention on sensation and perception. Much less is known about how attention impacts the acquisition and activation of high-level information in the brain. Here, we use machine learning of EEG and concurrently-recorded EEG/MRI to temporally and anatomically characterise the neural network that abstracts from attended perceptual information to activate and construct semantic and conceptual representations. We find that the trial-wise amplitude of N2pc - an ERP component closely linked to selective attention - predicts the rapid emergence of information about semantic categories in EEG. Similar analysis of EEG/MRI shows that N2pc predicts MRI-derived category information in a network including VMPFC, posterior parietal cortex, and anterior insula. These brain areas appear critically involved in the attention-mediated translation of perceptual information to concepts, semantics, and action plans.

neuroscience↗